<style>

    #ball {
        width: 100px;
        height: 100px;
        margin: 50px auto;
        position: relative;
        border-radius: 50%;
        background: linear-gradient(
            35deg,
            #ccffff,
            #ffcccc
        );
        animation-name: bounce;
        animation-duration: 1s;
        animation-iteration-count: infinite;
    }

    @keyframes bounce{
        0% {
            top: 0px;
        }
        50% {
            top: 249px;
            width: 130px;
            height: 70px;
        }
        100% {
            top: 0px;
        }
    }
</style>
<div id="ball"></div>